First Evidence of Water Vapor at Jupiter’s Moon Ganymede

This image presents Jupiter's moon Ganymede as seen by the Hubble Space Telescope in 1996. Ganymede is located half a billion miles (over 600 million km) away, and Hubble can follow changes on the moon and reveal other characteristics at ultraviolet and near-infrared wavelengths. Astronomers used new and archival datasets from Hubble to reveal evidence of water vapor in the atmosphere of Jupiter's moon Ganymede, which is present due to the thermal escape of water vapor from the moon's icy surface. Understanding the Jovian system and unravelling its history, from its origin to the possible emergence of habitable environments, will provide us with a better understanding of how gas giant planets and their satellites form and evolve. In addition, new insights will hopefully be found on the habitability of Jupiter-like exoplanetary systems.